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Status and population characteristics of the northern river otter (Lontra canadensis) in central and eastern Oklahoma

2800.3 P438
-158-R 2/05-1/08
FINAL PERFORMANCE REPORT
State: Oklahoma Grant Number: W-158-R
Grant Program: Wildlife Restoration
Grant Title: Status and population characteristics of the northern river otter (Lontra
canadensis) in central and eastern Oklahoma
Grant Period: February 1, 2005 - January 31, 2008
Report Period: February 1. 2007 - January 31, 2008
Project Leader: David M. Leslie
Objective:
To evaluate current distribution and population status of the northern river otter where they have
been reportedly observed in the past 20 years, mamly in central and eastern Oklahoma.
Summary of Progress:
Attached Master's Thesis serves as our final report.
Prepared by: Dominic Barrett
Date: March 31, 2008
Approved by:
Wildlife Division Admini ation
Oklahoma Department of Wildlife Conservation
J D. Staford
ed ral Aid Coordinator
ahoma Department of Wildlife Conservation
STATUS AND POPULATION CHARACTERISTICS
OF THE NORTHERN RIVER OTTER (LONTRA
CANADENSIS) IN CENTRAL AND
EASTERN OKLAHOMA
Thesis Approved:
David M. Leslie, Jr.
Thesis Advisor
Craig A. Davis
William L. Fisher
A. Gordon Emslie
Dean ofthe Graduate College
ii
ACKNOWLEDGMENTS
Funding for this research was provided by the Federal Aid, Pittman-Robertson
Wildlife Restoration Act under Project W-158-R of the Oklahoma Department of
Wildlife Conservation and Oklahoma State University. The project was administered
through the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma
Department of Wildlife Conservation, United States Geological Survey, Oklahoma State
University, Wildlife Management Institute, and United States Fish and Wildlife Service
cooperating). This research was partially supported by the National Science Foundation
Louis Stokes Alliance for Minority Participation Bridge to Doctorate Program under
grant number HRD-0444082.
In addition to financial contributors, I would like to thank my family and friends
for always supporting me. Without them, I am not sure I would have continued my path
and conquered the obstacles placed before me. I thank my Dad for introducing me to the
outdoors and showing me a great appreciation for everything natural. I thank my Mom
for her friendship and willingness to listen no matter what the circumstance.
Thank you to Stacey K. Davis and Ashley A. Foster for their assistance in the
field and many hours of humorous conversation. I thank Dave Hamilton from the
Missouri Department of Conservation and Mike Fischer from the Arkansas Trappers
Association, for introducing me to the "fine art" of tracking and trapping river otters. I
also thank numerous private land owners across eastern Oklahoma for allowing me
access. I especially thank Mildred (Mig) Hamilton and Roger Canada for their
iii
hospitality and generosity. I thank several employees from the Oklahoma Department of
Wildlife Conservation and United States Fish and Wildlife Service for their aid in
pursuing such an intimidating task. I want to thank Sheryl Lyon, Joyce Hufford, and
Judy Gray for their assistance. Last but not least, I would like to thank my committee
members, Craig A. Davis and William L. Fisher, for their support and guidance. In
particular, I appreciate my advisor, David (Chip) M. Leslie, Jr., for providing me this
opportunity, constant encouragement, inspiration, and an open door. I thank you all for
your time and efforts.
IV
TABLE OF CONTENTS
Chapter Page
1. CURRENT DISTRIBUTION OF AN EXPANDING RIVER OTTER
(LONTRA CANADENSIS) POPULATION
Abstract. 1
Introduction 2
Materials and Methods 5
Results 11
Discussion 14
Acknowledgments 18
Literature Cited 19
Tables 33
Figures 34
2. SPA TIOTEMPORAL AGE STRUCTURES AND POPULATION
CHARACTERISTICS OF A PARTIALLY REESTABLISHED RIVER OTTER
(LONTRA CANADENSIS) POPULATION
Abstract. 37
Introduction 38
Materials and Methods 42
Results 48
Discussion 51
Acknowledgments 60
v
Literature Cited 61
Tables 75
Figures 78
APPENDIX 85
vi
LIST OF TABLES
Table Page
Chapter I
1. River otter mail survey statistics based upon return rates of individual
groups of survey participants (2006). . 33
Chapter II
1. Comparison of the percentage of juveniles and adults in river otter
populations by state or province (adapted from Gallagher 1999 and
Polechla 1987) 75
2. Isotopic signatures of river otter liver (n = 24), muscle (n = 25), toenail (n
= 49), and teeth (n = 52; 2005-2007); samples categorized by trap site
(pre- and post-1996 counties) 76
3. Isotopic signatures of river otter toenail (n = 49) and teeth (n = 48; 2005-
2007); samples categorized by watershed (Illinois River Watershed
[ILRW], n = 13,8; Arkansas River Watershed [ARRW], n = 12, 18;
Canadian River Watershed [CRW], n = 4,6; and Red River Watershed
[RRW], n = 20, 16) 77
VII
LIST OF FIGURES
Figure Page
Chapter I
1. Watersheds and their percentages of positive sites for river otters during
sign surveys, winter and spring, 2006-2007 .34
2. Changing occurrence of river otters in Oklahoma counties, through 2007..... .35
3. Oklahoma counties where river otters have been captured by USDA
Animal and Plant Health Inspection Service employees; year within each
county (1991-2007) represents first year of capture. . 36
Chapter II
1. Oklahoma counties where river otters have been captured by USDA
Animal and Plant Health Inspection Service employees; year within each
county (1991-2007) represents first year of capture. . 78
2. River otter capture sites (n = 58) within pre- (empty circles) and post-1996
(shaded circles) counties (2005-2007) 79
3. River otter capture sites from the Arkansas River and its tributaries and
within, A) 70, 140, and 210 km, and B) 100 and 200 km of Arkansas state
border (2005-2007). . 80
4. River otter capture sites within 4 watersheds in eastern Oklahoma
(2005-2007). . 81
5. Age distribution of river otters captured by USDA APHIS and
OKCFWRU in Oklahoma and collected by ODWC employees (2005-
2007) 82
6. Age distribution of river otters captured in pre- and post-1996 counties in
eastern Oklahoma (2005-2007) 83
7. Relationship between mean and age years since initial capture of river
otters in Oklahoma, 1991-2007 84
viii
APPENDICES
Appendix Page
A. Mail survey and distributional questionnaire (2005). . 85
B. Institutional Review Board letter and approval form. . 88
C. Locations of sign survey sites visited in winter and spring 2006 and 2007;
river otters and/or sign was recorded as present (P) or absent (A) and sites
that did not contain water were not searched (NW). . 89
D. Watersheds of eastern Oklahoma 104
E. River otter death report (2005). . 105
F. Stable istotope signatures (813C, 815N) of river otter liver, muscle, toenail,
and teeth from pre- and post-1996 counties (2005-2007). . 107
G. Stable isotope signatures (813C, 81~) of river otter toenails and teeth from
4 watersheds (Illinois River Watershed [ILRW], Arkansas River
Watershed [ARRW], Canadian River Watershed [CRW], Red River
Watershed [RRW]) in eastern Oklahoma (2005-2007) 111
H. River otter capture data from eastern Oklahoma (2006, 2007). . .1-13
I. Comparison of capture data (catch per unit effort) by state 114
IX
CHAPTER I
DISTRIBUTION OF AN EXPANDING RIVER OTTER
(LONTRA CANADENSIS) POPULATION
ABSTRACT
In 1984 and 1985, the Oklahoma Department of Wildlife Conservation
reintroduced northern river otters (Lontra canadensis) in eastern Oklahoma. As a result
of reintroduction efforts and immigration from Arkansas, river otters have become
reestablished throughout eastern Oklahoma. In the past, distributional data have been
limited to incidental harvest by state and federal trappers and roadkills collected
opportunistically. Our goal was to determine the precise distribution of river otters in
Oklahoma via sign surveys and mail surveys. During winter and spring of 2006 and
2007, we visited 340 bridge sites within 28 different watersheds and identified river otter
signs in 11 counties where river otters were not previously documented. Approximately
300 (27%) mail surveys were returned by state and federal natural resource employees,
private organizations, and professional and recreational trappers. Mail surveys revealed
the possibility of river otters occurring in 8 additional counties where they were not
documented previously by published literature, USDA Animal and Plant Health
Inspection Service records, or by sign survey efforts.
Key words: distribution, Lontra canadensis, mail survey, northern river otter, sign
survey, sightings, track survey
INTRODUCTION
Prior to European settlement and westward expansion, northern river otters
(Lontra canadensis; hereafter "river otter") inhabited much ofthe U.S. and were found in
all major rivers of North America (Anderson 1977; Hall 1981). River otters were
documented throughout Oklahoma except in the Panhandle (Duck and Fletcher 1944).
However, because of habitat destruction, human settlement, unregulated harvest, and
water pollution, river otter populations became severely depleted or extirpated in much of
their historic range by the early 1900s (Toweil and Tabor 1982; Jenkins 1983; Lariviere
and Walton 1998). River otters were extirpated in 7 states and severely depleted in 9
other states including Oklahoma (Raesly 2001; Melquist et al. 2003). As a result, river
otters have been protected by Oklahoma state law since 1917. Between 1917 and 1971,
there were only 4 documented accounts of river otters in Oklahoma (Hatcher 1984).
Due to habitat improvement, construction of reservoirs, wetland restoration,
recent reintroduction efforts, and management, river otters have returned to 90% of their
historical range in the U.S. (Melquist et al. 2003). Moreover, increases in populations of
2
beaver (Castor canadensis) and associated creation of wetland habitats across the u.s.
provide river otters additional habitat in areas with limited resources (Jenkins 1983;
Swimley et al. 1999). Habitat use by river otters is partially contingent upon shelter
availability (Reid et al. 1994); river otters do not excavate their own dens (Melquist et al.
2003) and often occupy beaver lodges and bank dens (Melquist and Hornocker 1983).
Within Oklahoma, about 250,000 ponds and 145 major reservoirs have been
constructed since the 1930s (Schackelford and Whitaker 1997). In addition, >130
wetlands in Oklahoma have been restored by the Wetland Reserve Program ofthe U.S.
Department of Agriculture (USDA) Natural Resource Conservation Service and in
cooperation with other agencies (S. Tully, pers. comm. 2005). Ponds (Reid et al. 1988),
reservoirs (Sheldon and Toll 1964), and restored wetlands (Polechla 1987; Newman and
Griffin 1994) provide additional habitat for river otters.
In 1984 and 1985, the Oklahoma Department of Wildlife Conservation (ODWC)
released 10 river otters at Wister Wildlife Management Area (WMA) in Leflore County
and 7 river otters at McGee Creek WMA in Atoka County (Base 1986); all translocated
river otters were purchased in coastal Louisiana (Bayou Otter Farm, Theriot, Louisiana,
USA). During a 2-year period throughout the mid-to-Iate 1990s, 22 river otters were
released at the Wichita Mountains Wildlife Refuge (WMWR) in Comanche County. Six
river otters reintroduced to WMNWR were obtained from Louisiana (Bayou Otter Farm);
the remaining 16 were captured by USDA Animal and Plant Health Inspection Service
(APHIS) employees near Tahlequah, Oklahoma (R. Smith, ODWC, pers. comm. 2005).
Since the mid-1970s, river otter numbers in Oklahoma have increased probably due to
immigration from increasing populations in Arkansas (Hatcher 1984) and relocation
3
efforts within Oklahoma. Dispersing river otters can move up to 42 km in 1 day
(Melquist and Hornocker 1983). Base (1986) reported that accidental trappings and
observations of river otters commonly occurred along the Fouche Maline, lower Arkansas
River tributaries, Mountain Fork, Poteau River, and Sans Bois Creek in southeastern
Oklahoma. In general, the annual number of river otters accidentally captured in
Oklahoma by APHIS employees pursuing beavers (Castor canadensis) has increased (J.
Steuber, pers. comm. 2005).
Oklahoma has 126,459 km of streams and rivers, 18,686 km of shoreline, and
290,078 ha of surface water (http://www.owrb.ok..gov/util/waterfact.php, accessed 5
January 2008). Because river otters are capable of occupying many different aquatic
environments (Mech 2002; Melquist et al. 2003), it is likely that many of Oklahoma's
water bodies are suitable otter habitat and capable of sustaining river otter populations
(Caire et al. 1989). However, no formal study has been conducted to assess
contemporary distribution of river otters in Oklahoma. Shackelford and Whitaker (1997)
examined habitat and relative abundance of river otters in the Little River, Poteau River,
and Sans Bois Creek drainages in southeastern Oklahoma. Determining distribution is a
fundamental part of conservation planning, and Macdonald (1990) noted that field
surveys are an essential tool in designing conservation programs for otters.
We used mail surveys and sign surveys to examine river otter distribution in
Oklahoma. During winter and spring 2006 and 2007, we conducted river otter sign
surveys throughout 28 watersheds in eastern and central Oklahoma. Mail surveys were
sent to state and federal natural resource employees, private organizations, and private
and professional trappers in 2006.
4
MATERlALS AND METHODS
River otters are difficult to observe because they are generally nocturnal
(Melquist and Hornocker 1983) and occur at low densities (Melquist and Hornocker
1983; Foy 1984; Shirley et al. 1988). Most researchers recommend using> 1 method to
monitor river otters (Melquist and Dronkert 1987; Chilelli et al. 1998; Gallagher 1999).
Methods used by researchers to examine otter (Lutrinae) distribution and other
parameters (e.g., density) have included carcass collection (Polechla 1987; Gallagher
1999), fecal DNA analysis (Dallas et al. 2003; Hansen 2004; Hung et al. 2004), infrared
technology (Garcia de Leaniz et al. 2006), population models (Hamilton 1998; Gallagher
1999; Woolf and Nielson 2001), radiotelemetry studies (Reid et al. 1994; Sjoasen 1997;
Durbin 1998; Perrin and Carranza 2000), and radiotracer implants (Shirley et al. 1988;
Testa et al. 1994).
Indirect methods used to examine river otters include sign surveys (Robson 1982;
Zackheim 1982; Foy 1984; Karnes and Tumlison 1984; Clark et al. 1987; Eccles 1989;
Mack et al. 1994; Shackelford and Whitaker 1997; Gallagher 1999; Bischof2003; Bluett
et al. 2004), aerial snow-track surveys (Reid et al. 1987; St-Georges 1995), scent-station
indices (Humphrey and Zinn 1982; Robson and Humphrey 1985; Clark et al. 1987),
latrine-site surveys (Karnes and Tumlison 1984; Newman and Griffin 1994), otter harvest
surveys (Chilelli et al. 1996; Gallagher 1999; Scognamillo 2005), and mail surveys
inquiring about distributional and status information (Zackheim 1982; Blumberg 1993;
Kiesow 2003). Sign surveys are more cost-effective and likely to detect otter presence
than scent-station surveys (Robson and Humphrey 1985; Clark et al. 1987; Eccles 1989).
5
North American river otters have been described as an "ecological equivalent" to
Eurasian otters (Lutra lutra; Chanin 1985), and researchers outside of North America and
Europe have used sign surveys to examine other species of otter (Lutrinae; Chehebar
1985; Lee 1996). Studies involving documentation of otter signs (e.g., scat, tracks,
latrines) are commonly used on other continents including Africa (Macdonald and Mason
1983a, 1984; Rowe-Rowe 1992; Carugati and Perrin 2006), Asia (Lee 1996; Anoop and
Hussain 2004; Shenoy et al. 2006), Europe (Romanowski 2006; MacDonald et al. 2007;
Prigioni et al. 2007; Sulkava and Luikko 2007), and South America (Chehebar 1985;
Medina-Vogel et al. 2003). Within North America, documentation of river otter sign has
been used to determine distribution (Chromanski and Fritzell 1982), habitat preferences
(Dubuc et al. 1990; Newman and Griffin 1994), population size (Reid et al. 1987), and
relative abundance (Shackelford and Whitaker 1997; Gallagher 1999).
Sign surveys.-Sign surveys were conducted in the vicinity of bridges
(Shackelford and Whitaker 1997), low-water crossings, and locations where flowing
water was adjacent to roadways or access points (Lode 1993; Romanowski et al. 1996).
Examining bridges does not affect chances of detecting river otter presence (Gallant
2007). Sign surveys were conducted in 28 watersheds in eastern and central Oklahoma
on private, state, and federal lands. Riparian vegetation varied from native grasses along
prairie streams to oak (Quercus)-hickory (Carya) dominated forest further east. Stream
substrates ranged from clay to bedrock with more rocky substrates occurring in eastern
areas.
Using ArcMap 9.1 (Environmental Systems Research Institute, Inc., Redlands,
California, USA), we selected sites along ~ 3rd order streams (Swimley et al. 1999;
6
Kiesow and Dieter 200S); sites were j, 8-16 km stream km apart (Shackelford and
Whitaker 1997). Originally, sign surveys were conducted at::: 8 km intervals; however,
to conserve time and increase efficiency, survey distance was increased to::: 16 km.
Larger streams (i.e., streams with greater length and higher order) were given priority
over smaller streams (Dubuc et al. 1990). Extremely large rivers (e.g., ::: s" order) that
were canalized and lacked suitable latrine sites were not sampled (Romanowski et al.
1996). Bridge sites with steep banks >4So (Gallagher 1999) and:::: 16 stream km were not
sampled (Shackelford and Whitaker 1997). Mean linear home ranges of reintroduced
river otters in southeastern Oklahoma were> 16 km (Base 1986). Therefore, it is likely
that a home range would overlap with 1-2 sample points (Chanin 2003). Sites within
residential areas were not sampled. No sites were sampled within 3 days of measurable
precipitation (> 0.2 em) or a high water event (Clark et al. 1987; Shackelford and
Whitaker 1997), and each site was visited once. Because of time constraints and limited
manpower, we were not able to visit sample sites twice.
Sign surveys were conducted from January to May 2006 and January to June
2007 (Shirley et al. 1988; Gallagher 1999; Shackelford 1994) because river otter activity
levels (corresponding with mating season) are greatest during winter (Foy 1984) and
spring (Melquist and Hornocker 1983). Sign surveys were continued until June 2007
because record high precipitation and unusually high water levels prevented field work
after that. Using USGS Real-Time Water Data (http://waterdata.usgs.gov/ok/nwis/rt),
efforts were made to sample streams and rivers when discharge was between 2Sth and 7Sth
percentile of that sampling date. We did not search sites where nonhydrophytic
vegetation within or near the streambed was inundated or where no water was present.
7
We intensively searched both sides of streams for otter sign throughout 4 belt
transects (Elmeros and Bussenius 2002) of 200 x 5 m upstream and downstream of each
bridge, low-water crossing, or access point (Mason and Macdonald 1987; Shackelford
1994; Romanowski et al. 1996). Sites containing beaver bank dens and lodges (Swim ley
et al. 1999; Karnes and Tumlison 1984), beaver scent mounds (Karnes and Tumlison
1984), points ofland (Dubuc et al. 1990; Newman and Griffin 1994; Swimley et al.
1998), isthmuses, mouths of perennial streams (Newman and Griffin 1994), logjams
(Melquist and Hornocker 1983), elevated debris-covered banks (Karnes and Tumlison
1984), and islands (Mowbray et al. 1976; Swimley 1996) were examined closely because
river otters prefer such areas for latrines. River otters deposit feces, anal sac secretions,
and urine on latrine sites (Swimley 1996). Personnel conducting sign surveys were
trained by experienced employees from the Missouri Department of Wildlife
Conservation (Evans 2006).
Presence or absence of river otters and first type of sign observed were recorded.
Positive sites were identified as those where river otters were observed and/or sign was
identified. Positive sites confirmed the presence of river otters in the searched area. We
used Pearson's Chi-square analysis to examine differences in proportion of positive sites
among watersheds (Fusillo et al. 2007). Analysis included completed watersheds and
those that contained> 5 examined sites (n = 21). Latrines were defined by the presence
of~ 1 scat. Regression analyses were used to evaluate the relationship between years
since initial capture and the proportion of positive sites from each county. Channel
habitat variables were recorded at each identified latrine site. Sample sites were given a
detectability rating based on the proportion oftrackable substrate, such as exposed banks
8
and sandbars, and searchability (Gallagher 1999). Trackability was determined by visual
estimation of the percentage oftrackable substrate and was compared between negative
and positive sites using a 2-tailed t-test (n = 294). Number of suitable latrine sites at each
sample location were recorded and compared between negative and positive sites using a
2-tailed t-test (n = 126). Search efforts at each sample site ended ifriver otters were
observed or sign was detected; no efforts were made to quantify river otter sign because
previous research did not find a correlation between numbers of scats and river otters
(Jenkins and Burrows 1980; Kruuk et al. 1986). Investigating and quantifying only scat
can be problematic (Gallant et al. 2007), but regions with mild climates and limited snow
fall do not permit use of other methods (e.g., snow track surveys). All statistical tests
were conducted using SYSTAT 10 for Windows (SPSS Inc., Chicago, Illinois) and were
considered significant at P < 0.05.
Mail surveys.-Although collection localities of museum specimens can be used
to determine distribution, such methods can be inaccurate. For example, some species
are underrepresented and are collected rarely (Hazard 1982; Blumberg 1993). Sighting
information also can be used to provide further information. Human-based surveys
seeking information on distribution and status of a species are often used and provide
useful information when managing species at large spatial scales (Hubbard and Serfass
2004; Lindsey et al. 2004; Stubblefield and Shrestha 2007). Researchers have used mail
surveys and questionnaires to examine distribution of river otters (Chromanski and
Fritzell 1982; Zackheim 1982; Blumberg 1993; Mack et al. 1994; Kiesow 2003, Bluett et
al. 2004) and other carnivores (Quinn 1995; Clark et al. 2002). Mail surveys are
9
inexpensive and efficient when obtaining distributional data throughout a large area
(Sommer and Sommer 1991).
We developed a mail survey questionnaire (Appendix A) to obtain information on
distribution of river otters in Oklahoma (Oklahoma State University Institutional Review
Board Application No. AS06l; Appendix B). Some questions were modified from Pike's
(1997) survey on mountain lions (Puma concotor+ Pike et al. 1999). Survey recipients
were asked to report river otter sightings and river otter sign that they observed during the
last 5 years (2001-2005). Recipients also were asked to identify locations of sightings by
placing a symbol on an enclosed map.
Mail surveys (n = 1,153) were sent to state and federal biologists and technicians
(ODWC, US Fish and Wildlife Service, USDA Forest Service), ODWC game wardens,
USDA APHIS employees, US Army Corps of Engineers lake managers and park rangers,
Nature Conservancy land stewards, and professional and recreational trappers. Mail
surveys were also sent to professional and recreational trappers who purchased a trapping
license in 2004-2005 and lived east ofInterstate 35. Survey groups were selected based
on knowledge and interest in the subject. To increase participation, survey participants
remained anonymous and were not asked to identify themselves. Pre-paid postage and
pre-addressed return envelopes also were included with the survey (Blumberg 1993).
Returned surveys were organized by employer or affiliation (Pike et al. 1999). Because
we could not identify nonrespondants, a follow-up reminder was sent to all survey
recipients approximately 2 months after initial mailing (Filion 1978).
River otter "death reports" were mailed to ODWC regional biologists and game
wardens that opportunistically collected carcasses. Death reports were designed to
10
acquire additional data on river otter distribution and facilitate specimen collection.
Recipients were asked to report location (water body, town, county) and general habitat
charactersistcs. APHIS employees conducting damage control associated with beaver
activity also received "death reports." River otters are often harvested incidentally by
trappers pursuing beavers (Gallagher 1999; Bischof2003) using non-selective Conibear
330 traps (Hill 1976).
RESULTS
Sign surveys.-We visited 340 riparian reaches throughout eastern and central
Oklahoma (Appendix C, D), but 43 sites were not examined because water was not
present. We observed river otters or identified river otter sign at 159 of297 (53.5%) of
all examined sites. Of 159 positive sites, we observed river otters at 2 sites, identified
tracks at 20 sites, and latrines at 137 sites. Proportion of positive sites within each
watershed was 0-100% (Fig. 1). There was a significant difference (X2 = 123.81; df= 20;
P < 0.001) in proportion of positive sites among completed watersheds. During the sign
surveys, we identified river otter sign in 11 counties (Carter, Cleveland, Kay, Lincoln,
Okfuskee, Osage, Ottawa, Pontotoc, Pottawatomie, Rogers, Tulsa; Fig. 2) where river
otters have not been documented in published literature (Caire et al. 1989) or by APHIS
records. Sign surveys documented river otter sign in all counties where they were
captured by APHIS. Proportion of positive sites within each county were correlated
positively (r2= 0.57; P < 0.05) with number of years of since initial capture.
River otter sign was located along the Little River in Pottawatomie County off of
US Route 177. Because the latrine occurred beyond the standard 200 m, the sample site
11
was considered negative. One latrine was identified opportunistically along the Arkansas
River below Kaw Lake on the border between Kay and Osage counties. River otter signs
also were identified opportunistically along the North Canadian River in Mcintosh and
Okfuskee counties near Indian Nation Turnpike bridge. Two sites were searched
opportunistically within the Lower Cimarron Watershed, but no river otter sign was
documented. Middle Washita River and Muddy Boggy Creek watersheds were not
completed because time constraints and high water levels. River otter sign was
documented on Caddo Creek within the Middle Washita River Watershed (Carter
County). River otter sign also was documented at 3 examined sites in the Muddy Boggy
Creek Watershed.
Elk River and Bois D'arc Creek-Island Bayou watersheds were not sampled.
Because the majority ofthe Elk River Watershed occurs in western Arkansas, only one
sample site was selected along the Elk River in Delaware County, Oklahoma, but it was
not examined because water was not present. Bois D'arc Creek and Island Bayou
Watershed, primarily in Bryan County, was not sampled because no suitable sample sites
were located near bridges or access points. All streams within that watershed were small
(i.e., < 1 m) or highly entrenched (i.e., >450 banks). Because streams and rivers tended to
be more entrenched further west, we located fewer suitable sample sites and, therefore,
examined fewer sites in western watersheds. Over 150 sites were removed from the
sample because steep banks dominated the shoreline.
Trackability of negative sites (X = 4.10) and positive sites (X = 3.23) differed (t
= 3.81; P < 0.001). There was no difference (t = 1.79; P> 0.05) between number of
suitable latrine sites located at negative and positive sites. Within positive sites, 56.5% of
12
river otter sign occurred within the first 100 m (X = 93.3 m). Less than 21% oflatrines
occurred after 150 m. Most latrines (59.2%) were located within 50 m ofa transition
between channel habitat variables. Of latrines occurring within 50 m of a stream habitat
transition, approximately 75.6% occurred at a transition between pools (main channel,
comer, lateral scour, and confluence) and other stream habitat types. Most commonly
(74.6%), the transition occurred between pool and riffle (low and high gradient) habitats.
Most latrines were located at the bankfull step (64.3%; Rosgen 1996) along straight
shorelines (53.9%) with vertical (53.8%) or sloped (31.9%) banks. Latrines commonly
occurred near slack water where detritus accumulated within the streambed (33.3%),
areas inhabited by beavers (76.9%), and within 50 m of tributaries (21.2%). The mean
stream width adjacent to latrines was 22.8 m.
Mail surveys.- Twenty-seven percent of 1,153 mail surveys were returned.
Return rates among surveyed groups were 0--46% (Table 1). Thirty-nine percent of all
returned surveys reported observing river otters within the last 5 years (2001-2005).
Twenty-eight percent of all returned surveys reported observing river otter sign within the
last 5 years. Overall, the number of reported river otter sightings and observations of
sign among all groups increased from 22 to 89 and 11 to 62, respectively, during the past
5 years. Survey participants reported river otters in 19 new counties (Fig. 2). State and
federal wildlife employees reported river otters in 6 new counties (Cotton, Marshall,
Okfuskee, Pontotoc, Pottawatomie, and Tulsa). River otter death reports documented
otters in 2 new counties (Okfuskee and Tulsa). Mail survey participants identified all
counties where river otters were captured by APHIS employees except Creek and
Seminole counties. Six new counties were reported by> 1 survey group (Carter,
13
Marshall, Okfuskee, Pontotoc, Pottawatomie, and Tulsa). Locations of river otter
sightings or observance of sign was similar among survey groups. Most sightings and/or
signs occurred in localized areas (e.g., reservoirs) with high accessibility. Mail survey
participants reported river otters throughout all counties identified by sign survey efforts.
Combined, sign surveys and mail survey participants found river otters in 19 new
individual counties (Fig. 2; Caire et al. 1989), and eight ofthose counties were not
identified by sign surveys.
DISCUSSION
Mason and Macdonald (1987) noted a positive correlation (r2 = 0.84; P < 0.01)
between the mean number of scats and the proportion of positive sites from each study
area. Unlike others (Jenkins and Borrows 1980; Kruuk et al. 1986), Mason and
Macdonald (1987) noted that scats can be used to make a broad comparison among
populations. Nevertheless, the validity of using scats to determine otter (Lontra spp,
Lutra spp.) occurrence is still debated (Gallantet al. 2007), but researchers throughout
Europe continue to examine scats and proportions of positive sites to compare otter
densities (Fusillo et al. 2007; MacDonald et al. 2007).
Indirect signs are often effective tools to study wildlife species (Plumptre 2000;
Sadlier et al. 2004; Stephens et al. 2006). However, caution should be used when
interpreting river otter sign data (Rostain 2000; Gallagher 1999) because several factors
can affect detection (Evans 2006, Fusillo et al. 2007); for instance, occupants could be
outside of the sampled area but within its home range. Presence can often be determined,
but absence can be impossible to determine (MacKenzie 2005). Others have reported
14
that there is not always a relationship between number of scats and number of river otters
(Jenkins and Burrows 1980; Melquist and Hornocker 1983; Kruuk and Conroy 1987;
Gallagher 1999; Gallant et al. 2007). Furthermore, sites with less scat could be an
indication of fewer suitable latrine habitats (Romanowski et al. 1996). In contrast, we
determined that no difference occurred between the number of suitable latrine sites at
positive and negative sites.
Because oftime constraints and high water levels, we did not sample Lower
Canadian River and Walnut Creek and Lower North Canadian River watersheds.
However, mail surveys, "death reports," and APHIS records documented river otters
within both ofthese drainages. Sign surveys were conducted within the Little River
Watershed, a tributary to the Canadian River in central Oklahoma. River otter sign was
documented along the Little River in Pottawatomie County and below Lake Thunderbird
in Cleveland County. To reach these locations, river otters must have used the Canadian
River above Eufaula Lake. Within the Lower North Canadian River Watershed, we
collected 1 river otter carcass and identified river otter signs above Eufaula Lake along
the North Canadian River in McIntosh and Okfuskee counties.
We examined 3 sites within the Muddy Boggy Creek Watershed that contained
river otter sign. Most likely river otters have become well established throughout this
watershed because reintroduction efforts (McGee Creek WMA), suitable habitats, and
neighboring watersheds (Clear Boggy Creek Watershed, Kiamichi River Watershed)
contained relatively high proportions of positive sites (Fig. 1).
Mail surveys allowed us to obtain specific locations of river otters throughout
Oklahoma and were relatively inexpensive and required less time and effort than sign
15
surveys; however, data should be interpreted cautiously. Previous researchers surveyed
only natural resource employees because responses from outdoorsman were considered
unreliable (Van Dyke and Brocke 1987; McBride et al. 1993; Pike et al. 1999).
However, even natural resource professionals can be inaccurate when identifying animal
sign unless properly trained (Evans 2006). Within our study, Chi-square analysis
revealed that positive responses among surveyed groups (trappers, ODWC, federal
employees) did not differ ("l = 1.17; df= 2; P> 0.10). Regardless of who is surveyed,
researchers must account for issues regarding access; locations commonly visited by
outdoorsman and areas not accessible could influence distributional data (Stubblefield
and Shrestha 2007). Van Dyke and Brocke (1987) noted that human-based surveys
should not be used alone to describe distribution of mountain lions; instead; such surveys
should be used with other methods to determine spatial distribution. Mail survey
information should only be used as estimates of mammal distribution (Blumberg 1993).
Since the 1970s, river otters have become more prevalent throughout eastern
Oklahoma and continued to spread westward, recolonizing parts of their historic range
(Hatcher 1984; Base 1986). By 1992, APHIS employees reported catching river otters in
6 counties (Atoka, Haskell, Latimer, Leflore, McCurtain, Pushmataha) in southeastern
Oklahoma. Illustrating westward movement, river otters were unintentionally captured in
> 1 new county, on average, each year from 1991 to 2007 (Fig. 3), but the majority of
annual incidental captures by APHIS employees came from southeastern Oklahoma.
Currently, river otters have become well established and commonly occur throughout
most of eastern Oklahoma. Although we documented river otters in central Oklahoma, it
is unlikely that they occur at high densities throughout watersheds west of Blue River,
16
Clear Boggy Creek, and Lower Washita River watersheds and east ofWMNWR. Mail
surveys and APHIS harvest records showed few accounts of river otters in central
Oklahoma. Furthermore, sign surveys within Little River Watershed (central Oklahoma)
showed relatively low proportions of sites containing river otter sign (29%). Similarly,
29% of examined sites along upper portions of the Deep Fork Watershed were positive.
We suggest that no more than broad comparisons among large watersheds should
be made from the proportion of positive sites within a watershed (Macdonald 1987) and
management decisions should not be based solely on sign indices (Gallagher 1999).
Most importantly, sign surveys should be used to monitor sample sites throughout time to
document range expansion and/or reduction (Swimley and Hardisky 2000). Large
reductions in population size may be more evident when baseline data have been
recorded previously. Changes in scat frequency may be detectable only when otter
populations have been impacted greatly (Jenkins and Burrows 1980; Mason and
Macdonald 1987); for example, Lode (1993) used sign-surveys to document otter decline
in France. Sign surveys were used to document range expansion and recolonization in
Poland (Romanowski 2006). Other state wildlife agencies already use sign surveys to
monitor river otter distributions (Boyd 2006, Evans 2006).
Conducting systematic surveys is essential to species management and
conservation throughout time (Elmeros and Bussenius 2002; Gallant 2007) and should be
continued in Oklahoma. Within Oklahoma, relatively large watersheds such as Arkansas
River, Canadian River, Red River, Cimarron River, and Washita River, follow a west-to-east
pattern and facilitate westward dispersal and expansion of river otters. Studies using
indirect sign to examine river otter populations should consider detectability and repeated
17
visits to determine river otter presence or absence (Royle and Nichols 2003; MacKenzie
2005). Observer skill should also be evaluated using standardized methods (Evans 2006).
To achieve greater statistical power, the number of sites throughout each watershed
should be increased. In locations where suitable latrine sites do not exist, European
researchers have created artificial latrine sites to increase effectiveness of monitoring
efforts (Chanin 2003). Chanin (2003) recommended that sign surveys should be
conducted annually for 10 years, and then sampling should occur at intervals of2-3
years. Because sign surveys cannot detect annual fluctuations in river otter populations
(Clark et al. 1987; Gallagher 1999), we recommend visiting sites biennially until
variations (e.g., increase, decrease) cease. As baseline data and populations become
established, sampling intervals can be repeated less frequently.
ACKNOWLEDGMENTS
Funding for this research was provided by the Federal Aid, Pittman-Robertson
Wildlife Restoration Act under Project W-158-R ofthe Oklahoma Department of
Wildlife Conservation and Oklahoma State University. The project was administered
through the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma
Department of Wildlife Conservation, United States Geological Survey, Oklahoma State
University, Wildlife Management Institute, and United States Fish and Wildlife Service
cooperating). This publication was partially supported by the National Science
Foundation Louis Stokes Alliance for Minority Participation Bridge to Doctorate
Program under grant number HRD-0444082. We would like to thank S. K. Davis and A.
A. Foster for their assistance in the field. A special thanks to D. Hamilton from the
18
Missouri Department of Wildlife Conservation and M. Fischer from the Arkansas
Trappers Association for their guidance and training. We also thank R. Thornburg and S.
Sheffert of the Oklahoma Fur Bearers Alliance for their insight and assistance.
Numerous employees of the ODWC provided much needed assistance; we especially
thank A. Crews for helping develop the river otter survey. We thank hundreds of state
and federal employees and private and professional trappers who participated in the mail
survey. We thank hundreds of landowners across eastern Oklahoma who allowed
temporary access to their property. This project was completed as partial fulfillment for
the requirements of the degree of Master of Science.
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2800.3 P438
-158-R 2/05-1/08
FINAL PERFORMANCE REPORT
State: Oklahoma Grant Number: W-158-R
Grant Program: Wildlife Restoration
Grant Title: Status and population characteristics of the northern river otter (Lontra
canadensis) in central and eastern Oklahoma
Grant Period: February 1, 2005 - January 31, 2008
Report Period: February 1. 2007 - January 31, 2008
Project Leader: David M. Leslie
Objective:
To evaluate current distribution and population status of the northern river otter where they have
been reportedly observed in the past 20 years, mamly in central and eastern Oklahoma.
Summary of Progress:
Attached Master's Thesis serves as our final report.
Prepared by: Dominic Barrett
Date: March 31, 2008
Approved by:
Wildlife Division Admini ation
Oklahoma Department of Wildlife Conservation
J D. Staford
ed ral Aid Coordinator
ahoma Department of Wildlife Conservation
STATUS AND POPULATION CHARACTERISTICS
OF THE NORTHERN RIVER OTTER (LONTRA
CANADENSIS) IN CENTRAL AND
EASTERN OKLAHOMA
Thesis Approved:
David M. Leslie, Jr.
Thesis Advisor
Craig A. Davis
William L. Fisher
A. Gordon Emslie
Dean ofthe Graduate College
ii
ACKNOWLEDGMENTS
Funding for this research was provided by the Federal Aid, Pittman-Robertson
Wildlife Restoration Act under Project W-158-R of the Oklahoma Department of
Wildlife Conservation and Oklahoma State University. The project was administered
through the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma
Department of Wildlife Conservation, United States Geological Survey, Oklahoma State
University, Wildlife Management Institute, and United States Fish and Wildlife Service
cooperating). This research was partially supported by the National Science Foundation
Louis Stokes Alliance for Minority Participation Bridge to Doctorate Program under
grant number HRD-0444082.
In addition to financial contributors, I would like to thank my family and friends
for always supporting me. Without them, I am not sure I would have continued my path
and conquered the obstacles placed before me. I thank my Dad for introducing me to the
outdoors and showing me a great appreciation for everything natural. I thank my Mom
for her friendship and willingness to listen no matter what the circumstance.
Thank you to Stacey K. Davis and Ashley A. Foster for their assistance in the
field and many hours of humorous conversation. I thank Dave Hamilton from the
Missouri Department of Conservation and Mike Fischer from the Arkansas Trappers
Association, for introducing me to the "fine art" of tracking and trapping river otters. I
also thank numerous private land owners across eastern Oklahoma for allowing me
access. I especially thank Mildred (Mig) Hamilton and Roger Canada for their
iii
hospitality and generosity. I thank several employees from the Oklahoma Department of
Wildlife Conservation and United States Fish and Wildlife Service for their aid in
pursuing such an intimidating task. I want to thank Sheryl Lyon, Joyce Hufford, and
Judy Gray for their assistance. Last but not least, I would like to thank my committee
members, Craig A. Davis and William L. Fisher, for their support and guidance. In
particular, I appreciate my advisor, David (Chip) M. Leslie, Jr., for providing me this
opportunity, constant encouragement, inspiration, and an open door. I thank you all for
your time and efforts.
IV
TABLE OF CONTENTS
Chapter Page
1. CURRENT DISTRIBUTION OF AN EXPANDING RIVER OTTER
(LONTRA CANADENSIS) POPULATION
Abstract. 1
Introduction 2
Materials and Methods 5
Results 11
Discussion 14
Acknowledgments 18
Literature Cited 19
Tables 33
Figures 34
2. SPA TIOTEMPORAL AGE STRUCTURES AND POPULATION
CHARACTERISTICS OF A PARTIALLY REESTABLISHED RIVER OTTER
(LONTRA CANADENSIS) POPULATION
Abstract. 37
Introduction 38
Materials and Methods 42
Results 48
Discussion 51
Acknowledgments 60
v
Literature Cited 61
Tables 75
Figures 78
APPENDIX 85
vi
LIST OF TABLES
Table Page
Chapter I
1. River otter mail survey statistics based upon return rates of individual
groups of survey participants (2006). . 33
Chapter II
1. Comparison of the percentage of juveniles and adults in river otter
populations by state or province (adapted from Gallagher 1999 and
Polechla 1987) 75
2. Isotopic signatures of river otter liver (n = 24), muscle (n = 25), toenail (n
= 49), and teeth (n = 52; 2005-2007); samples categorized by trap site
(pre- and post-1996 counties) 76
3. Isotopic signatures of river otter toenail (n = 49) and teeth (n = 48; 2005-
2007); samples categorized by watershed (Illinois River Watershed
[ILRW], n = 13,8; Arkansas River Watershed [ARRW], n = 12, 18;
Canadian River Watershed [CRW], n = 4,6; and Red River Watershed
[RRW], n = 20, 16) 77
VII
LIST OF FIGURES
Figure Page
Chapter I
1. Watersheds and their percentages of positive sites for river otters during
sign surveys, winter and spring, 2006-2007 .34
2. Changing occurrence of river otters in Oklahoma counties, through 2007..... .35
3. Oklahoma counties where river otters have been captured by USDA
Animal and Plant Health Inspection Service employees; year within each
county (1991-2007) represents first year of capture. . 36
Chapter II
1. Oklahoma counties where river otters have been captured by USDA
Animal and Plant Health Inspection Service employees; year within each
county (1991-2007) represents first year of capture. . 78
2. River otter capture sites (n = 58) within pre- (empty circles) and post-1996
(shaded circles) counties (2005-2007) 79
3. River otter capture sites from the Arkansas River and its tributaries and
within, A) 70, 140, and 210 km, and B) 100 and 200 km of Arkansas state
border (2005-2007). . 80
4. River otter capture sites within 4 watersheds in eastern Oklahoma
(2005-2007). . 81
5. Age distribution of river otters captured by USDA APHIS and
OKCFWRU in Oklahoma and collected by ODWC employees (2005-
2007) 82
6. Age distribution of river otters captured in pre- and post-1996 counties in
eastern Oklahoma (2005-2007) 83
7. Relationship between mean and age years since initial capture of river
otters in Oklahoma, 1991-2007 84
viii
APPENDICES
Appendix Page
A. Mail survey and distributional questionnaire (2005). . 85
B. Institutional Review Board letter and approval form. . 88
C. Locations of sign survey sites visited in winter and spring 2006 and 2007;
river otters and/or sign was recorded as present (P) or absent (A) and sites
that did not contain water were not searched (NW). . 89
D. Watersheds of eastern Oklahoma 104
E. River otter death report (2005). . 105
F. Stable istotope signatures (813C, 815N) of river otter liver, muscle, toenail,
and teeth from pre- and post-1996 counties (2005-2007). . 107
G. Stable isotope signatures (813C, 81~) of river otter toenails and teeth from
4 watersheds (Illinois River Watershed [ILRW], Arkansas River
Watershed [ARRW], Canadian River Watershed [CRW], Red River
Watershed [RRW]) in eastern Oklahoma (2005-2007) 111
H. River otter capture data from eastern Oklahoma (2006, 2007). . .1-13
I. Comparison of capture data (catch per unit effort) by state 114
IX
CHAPTER I
DISTRIBUTION OF AN EXPANDING RIVER OTTER
(LONTRA CANADENSIS) POPULATION
ABSTRACT
In 1984 and 1985, the Oklahoma Department of Wildlife Conservation
reintroduced northern river otters (Lontra canadensis) in eastern Oklahoma. As a result
of reintroduction efforts and immigration from Arkansas, river otters have become
reestablished throughout eastern Oklahoma. In the past, distributional data have been
limited to incidental harvest by state and federal trappers and roadkills collected
opportunistically. Our goal was to determine the precise distribution of river otters in
Oklahoma via sign surveys and mail surveys. During winter and spring of 2006 and
2007, we visited 340 bridge sites within 28 different watersheds and identified river otter
signs in 11 counties where river otters were not previously documented. Approximately
300 (27%) mail surveys were returned by state and federal natural resource employees,
private organizations, and professional and recreational trappers. Mail surveys revealed
the possibility of river otters occurring in 8 additional counties where they were not
documented previously by published literature, USDA Animal and Plant Health
Inspection Service records, or by sign survey efforts.
Key words: distribution, Lontra canadensis, mail survey, northern river otter, sign
survey, sightings, track survey
INTRODUCTION
Prior to European settlement and westward expansion, northern river otters
(Lontra canadensis; hereafter "river otter") inhabited much ofthe U.S. and were found in
all major rivers of North America (Anderson 1977; Hall 1981). River otters were
documented throughout Oklahoma except in the Panhandle (Duck and Fletcher 1944).
However, because of habitat destruction, human settlement, unregulated harvest, and
water pollution, river otter populations became severely depleted or extirpated in much of
their historic range by the early 1900s (Toweil and Tabor 1982; Jenkins 1983; Lariviere
and Walton 1998). River otters were extirpated in 7 states and severely depleted in 9
other states including Oklahoma (Raesly 2001; Melquist et al. 2003). As a result, river
otters have been protected by Oklahoma state law since 1917. Between 1917 and 1971,
there were only 4 documented accounts of river otters in Oklahoma (Hatcher 1984).
Due to habitat improvement, construction of reservoirs, wetland restoration,
recent reintroduction efforts, and management, river otters have returned to 90% of their
historical range in the U.S. (Melquist et al. 2003). Moreover, increases in populations of
2
beaver (Castor canadensis) and associated creation of wetland habitats across the u.s.
provide river otters additional habitat in areas with limited resources (Jenkins 1983;
Swimley et al. 1999). Habitat use by river otters is partially contingent upon shelter
availability (Reid et al. 1994); river otters do not excavate their own dens (Melquist et al.
2003) and often occupy beaver lodges and bank dens (Melquist and Hornocker 1983).
Within Oklahoma, about 250,000 ponds and 145 major reservoirs have been
constructed since the 1930s (Schackelford and Whitaker 1997). In addition, >130
wetlands in Oklahoma have been restored by the Wetland Reserve Program ofthe U.S.
Department of Agriculture (USDA) Natural Resource Conservation Service and in
cooperation with other agencies (S. Tully, pers. comm. 2005). Ponds (Reid et al. 1988),
reservoirs (Sheldon and Toll 1964), and restored wetlands (Polechla 1987; Newman and
Griffin 1994) provide additional habitat for river otters.
In 1984 and 1985, the Oklahoma Department of Wildlife Conservation (ODWC)
released 10 river otters at Wister Wildlife Management Area (WMA) in Leflore County
and 7 river otters at McGee Creek WMA in Atoka County (Base 1986); all translocated
river otters were purchased in coastal Louisiana (Bayou Otter Farm, Theriot, Louisiana,
USA). During a 2-year period throughout the mid-to-Iate 1990s, 22 river otters were
released at the Wichita Mountains Wildlife Refuge (WMWR) in Comanche County. Six
river otters reintroduced to WMNWR were obtained from Louisiana (Bayou Otter Farm);
the remaining 16 were captured by USDA Animal and Plant Health Inspection Service
(APHIS) employees near Tahlequah, Oklahoma (R. Smith, ODWC, pers. comm. 2005).
Since the mid-1970s, river otter numbers in Oklahoma have increased probably due to
immigration from increasing populations in Arkansas (Hatcher 1984) and relocation
3
efforts within Oklahoma. Dispersing river otters can move up to 42 km in 1 day
(Melquist and Hornocker 1983). Base (1986) reported that accidental trappings and
observations of river otters commonly occurred along the Fouche Maline, lower Arkansas
River tributaries, Mountain Fork, Poteau River, and Sans Bois Creek in southeastern
Oklahoma. In general, the annual number of river otters accidentally captured in
Oklahoma by APHIS employees pursuing beavers (Castor canadensis) has increased (J.
Steuber, pers. comm. 2005).
Oklahoma has 126,459 km of streams and rivers, 18,686 km of shoreline, and
290,078 ha of surface water (http://www.owrb.ok..gov/util/waterfact.php, accessed 5
January 2008). Because river otters are capable of occupying many different aquatic
environments (Mech 2002; Melquist et al. 2003), it is likely that many of Oklahoma's
water bodies are suitable otter habitat and capable of sustaining river otter populations
(Caire et al. 1989). However, no formal study has been conducted to assess
contemporary distribution of river otters in Oklahoma. Shackelford and Whitaker (1997)
examined habitat and relative abundance of river otters in the Little River, Poteau River,
and Sans Bois Creek drainages in southeastern Oklahoma. Determining distribution is a
fundamental part of conservation planning, and Macdonald (1990) noted that field
surveys are an essential tool in designing conservation programs for otters.
We used mail surveys and sign surveys to examine river otter distribution in
Oklahoma. During winter and spring 2006 and 2007, we conducted river otter sign
surveys throughout 28 watersheds in eastern and central Oklahoma. Mail surveys were
sent to state and federal natural resource employees, private organizations, and private
and professional trappers in 2006.
4
MATERlALS AND METHODS
River otters are difficult to observe because they are generally nocturnal
(Melquist and Hornocker 1983) and occur at low densities (Melquist and Hornocker
1983; Foy 1984; Shirley et al. 1988). Most researchers recommend using> 1 method to
monitor river otters (Melquist and Dronkert 1987; Chilelli et al. 1998; Gallagher 1999).
Methods used by researchers to examine otter (Lutrinae) distribution and other
parameters (e.g., density) have included carcass collection (Polechla 1987; Gallagher
1999), fecal DNA analysis (Dallas et al. 2003; Hansen 2004; Hung et al. 2004), infrared
technology (Garcia de Leaniz et al. 2006), population models (Hamilton 1998; Gallagher
1999; Woolf and Nielson 2001), radiotelemetry studies (Reid et al. 1994; Sjoasen 1997;
Durbin 1998; Perrin and Carranza 2000), and radiotracer implants (Shirley et al. 1988;
Testa et al. 1994).
Indirect methods used to examine river otters include sign surveys (Robson 1982;
Zackheim 1982; Foy 1984; Karnes and Tumlison 1984; Clark et al. 1987; Eccles 1989;
Mack et al. 1994; Shackelford and Whitaker 1997; Gallagher 1999; Bischof2003; Bluett
et al. 2004), aerial snow-track surveys (Reid et al. 1987; St-Georges 1995), scent-station
indices (Humphrey and Zinn 1982; Robson and Humphrey 1985; Clark et al. 1987),
latrine-site surveys (Karnes and Tumlison 1984; Newman and Griffin 1994), otter harvest
surveys (Chilelli et al. 1996; Gallagher 1999; Scognamillo 2005), and mail surveys
inquiring about distributional and status information (Zackheim 1982; Blumberg 1993;
Kiesow 2003). Sign surveys are more cost-effective and likely to detect otter presence
than scent-station surveys (Robson and Humphrey 1985; Clark et al. 1987; Eccles 1989).
5
North American river otters have been described as an "ecological equivalent" to
Eurasian otters (Lutra lutra; Chanin 1985), and researchers outside of North America and
Europe have used sign surveys to examine other species of otter (Lutrinae; Chehebar
1985; Lee 1996). Studies involving documentation of otter signs (e.g., scat, tracks,
latrines) are commonly used on other continents including Africa (Macdonald and Mason
1983a, 1984; Rowe-Rowe 1992; Carugati and Perrin 2006), Asia (Lee 1996; Anoop and
Hussain 2004; Shenoy et al. 2006), Europe (Romanowski 2006; MacDonald et al. 2007;
Prigioni et al. 2007; Sulkava and Luikko 2007), and South America (Chehebar 1985;
Medina-Vogel et al. 2003). Within North America, documentation of river otter sign has
been used to determine distribution (Chromanski and Fritzell 1982), habitat preferences
(Dubuc et al. 1990; Newman and Griffin 1994), population size (Reid et al. 1987), and
relative abundance (Shackelford and Whitaker 1997; Gallagher 1999).
Sign surveys.-Sign surveys were conducted in the vicinity of bridges
(Shackelford and Whitaker 1997), low-water crossings, and locations where flowing
water was adjacent to roadways or access points (Lode 1993; Romanowski et al. 1996).
Examining bridges does not affect chances of detecting river otter presence (Gallant
2007). Sign surveys were conducted in 28 watersheds in eastern and central Oklahoma
on private, state, and federal lands. Riparian vegetation varied from native grasses along
prairie streams to oak (Quercus)-hickory (Carya) dominated forest further east. Stream
substrates ranged from clay to bedrock with more rocky substrates occurring in eastern
areas.
Using ArcMap 9.1 (Environmental Systems Research Institute, Inc., Redlands,
California, USA), we selected sites along ~ 3rd order streams (Swimley et al. 1999;
6
Kiesow and Dieter 200S); sites were j, 8-16 km stream km apart (Shackelford and
Whitaker 1997). Originally, sign surveys were conducted at::: 8 km intervals; however,
to conserve time and increase efficiency, survey distance was increased to::: 16 km.
Larger streams (i.e., streams with greater length and higher order) were given priority
over smaller streams (Dubuc et al. 1990). Extremely large rivers (e.g., ::: s" order) that
were canalized and lacked suitable latrine sites were not sampled (Romanowski et al.
1996). Bridge sites with steep banks >4So (Gallagher 1999) and:::: 16 stream km were not
sampled (Shackelford and Whitaker 1997). Mean linear home ranges of reintroduced
river otters in southeastern Oklahoma were> 16 km (Base 1986). Therefore, it is likely
that a home range would overlap with 1-2 sample points (Chanin 2003). Sites within
residential areas were not sampled. No sites were sampled within 3 days of measurable
precipitation (> 0.2 em) or a high water event (Clark et al. 1987; Shackelford and
Whitaker 1997), and each site was visited once. Because of time constraints and limited
manpower, we were not able to visit sample sites twice.
Sign surveys were conducted from January to May 2006 and January to June
2007 (Shirley et al. 1988; Gallagher 1999; Shackelford 1994) because river otter activity
levels (corresponding with mating season) are greatest during winter (Foy 1984) and
spring (Melquist and Hornocker 1983). Sign surveys were continued until June 2007
because record high precipitation and unusually high water levels prevented field work
after that. Using USGS Real-Time Water Data (http://waterdata.usgs.gov/ok/nwis/rt),
efforts were made to sample streams and rivers when discharge was between 2Sth and 7Sth
percentile of that sampling date. We did not search sites where nonhydrophytic
vegetation within or near the streambed was inundated or where no water was present.
7
We intensively searched both sides of streams for otter sign throughout 4 belt
transects (Elmeros and Bussenius 2002) of 200 x 5 m upstream and downstream of each
bridge, low-water crossing, or access point (Mason and Macdonald 1987; Shackelford
1994; Romanowski et al. 1996). Sites containing beaver bank dens and lodges (Swim ley
et al. 1999; Karnes and Tumlison 1984), beaver scent mounds (Karnes and Tumlison
1984), points ofland (Dubuc et al. 1990; Newman and Griffin 1994; Swimley et al.
1998), isthmuses, mouths of perennial streams (Newman and Griffin 1994), logjams
(Melquist and Hornocker 1983), elevated debris-covered banks (Karnes and Tumlison
1984), and islands (Mowbray et al. 1976; Swimley 1996) were examined closely because
river otters prefer such areas for latrines. River otters deposit feces, anal sac secretions,
and urine on latrine sites (Swimley 1996). Personnel conducting sign surveys were
trained by experienced employees from the Missouri Department of Wildlife
Conservation (Evans 2006).
Presence or absence of river otters and first type of sign observed were recorded.
Positive sites were identified as those where river otters were observed and/or sign was
identified. Positive sites confirmed the presence of river otters in the searched area. We
used Pearson's Chi-square analysis to examine differences in proportion of positive sites
among watersheds (Fusillo et al. 2007). Analysis included completed watersheds and
those that contained> 5 examined sites (n = 21). Latrines were defined by the presence
of~ 1 scat. Regression analyses were used to evaluate the relationship between years
since initial capture and the proportion of positive sites from each county. Channel
habitat variables were recorded at each identified latrine site. Sample sites were given a
detectability rating based on the proportion oftrackable substrate, such as exposed banks
8
and sandbars, and searchability (Gallagher 1999). Trackability was determined by visual
estimation of the percentage oftrackable substrate and was compared between negative
and positive sites using a 2-tailed t-test (n = 294). Number of suitable latrine sites at each
sample location were recorded and compared between negative and positive sites using a
2-tailed t-test (n = 126). Search efforts at each sample site ended ifriver otters were
observed or sign was detected; no efforts were made to quantify river otter sign because
previous research did not find a correlation between numbers of scats and river otters
(Jenkins and Burrows 1980; Kruuk et al. 1986). Investigating and quantifying only scat
can be problematic (Gallant et al. 2007), but regions with mild climates and limited snow
fall do not permit use of other methods (e.g., snow track surveys). All statistical tests
were conducted using SYSTAT 10 for Windows (SPSS Inc., Chicago, Illinois) and were
considered significant at P < 0.05.
Mail surveys.-Although collection localities of museum specimens can be used
to determine distribution, such methods can be inaccurate. For example, some species
are underrepresented and are collected rarely (Hazard 1982; Blumberg 1993). Sighting
information also can be used to provide further information. Human-based surveys
seeking information on distribution and status of a species are often used and provide
useful information when managing species at large spatial scales (Hubbard and Serfass
2004; Lindsey et al. 2004; Stubblefield and Shrestha 2007). Researchers have used mail
surveys and questionnaires to examine distribution of river otters (Chromanski and
Fritzell 1982; Zackheim 1982; Blumberg 1993; Mack et al. 1994; Kiesow 2003, Bluett et
al. 2004) and other carnivores (Quinn 1995; Clark et al. 2002). Mail surveys are
9
inexpensive and efficient when obtaining distributional data throughout a large area
(Sommer and Sommer 1991).
We developed a mail survey questionnaire (Appendix A) to obtain information on
distribution of river otters in Oklahoma (Oklahoma State University Institutional Review
Board Application No. AS06l; Appendix B). Some questions were modified from Pike's
(1997) survey on mountain lions (Puma concotor+ Pike et al. 1999). Survey recipients
were asked to report river otter sightings and river otter sign that they observed during the
last 5 years (2001-2005). Recipients also were asked to identify locations of sightings by
placing a symbol on an enclosed map.
Mail surveys (n = 1,153) were sent to state and federal biologists and technicians
(ODWC, US Fish and Wildlife Service, USDA Forest Service), ODWC game wardens,
USDA APHIS employees, US Army Corps of Engineers lake managers and park rangers,
Nature Conservancy land stewards, and professional and recreational trappers. Mail
surveys were also sent to professional and recreational trappers who purchased a trapping
license in 2004-2005 and lived east ofInterstate 35. Survey groups were selected based
on knowledge and interest in the subject. To increase participation, survey participants
remained anonymous and were not asked to identify themselves. Pre-paid postage and
pre-addressed return envelopes also were included with the survey (Blumberg 1993).
Returned surveys were organized by employer or affiliation (Pike et al. 1999). Because
we could not identify nonrespondants, a follow-up reminder was sent to all survey
recipients approximately 2 months after initial mailing (Filion 1978).
River otter "death reports" were mailed to ODWC regional biologists and game
wardens that opportunistically collected carcasses. Death reports were designed to
10
acquire additional data on river otter distribution and facilitate specimen collection.
Recipients were asked to report location (water body, town, county) and general habitat
charactersistcs. APHIS employees conducting damage control associated with beaver
activity also received "death reports." River otters are often harvested incidentally by
trappers pursuing beavers (Gallagher 1999; Bischof2003) using non-selective Conibear
330 traps (Hill 1976).
RESULTS
Sign surveys.-We visited 340 riparian reaches throughout eastern and central
Oklahoma (Appendix C, D), but 43 sites were not examined because water was not
present. We observed river otters or identified river otter sign at 159 of297 (53.5%) of
all examined sites. Of 159 positive sites, we observed river otters at 2 sites, identified
tracks at 20 sites, and latrines at 137 sites. Proportion of positive sites within each
watershed was 0-100% (Fig. 1). There was a significant difference (X2 = 123.81; df= 20;
P < 0.001) in proportion of positive sites among completed watersheds. During the sign
surveys, we identified river otter sign in 11 counties (Carter, Cleveland, Kay, Lincoln,
Okfuskee, Osage, Ottawa, Pontotoc, Pottawatomie, Rogers, Tulsa; Fig. 2) where river
otters have not been documented in published literature (Caire et al. 1989) or by APHIS
records. Sign surveys documented river otter sign in all counties where they were
captured by APHIS. Proportion of positive sites within each county were correlated
positively (r2= 0.57; P < 0.05) with number of years of since initial capture.
River otter sign was located along the Little River in Pottawatomie County off of
US Route 177. Because the latrine occurred beyond the standard 200 m, the sample site
11
was considered negative. One latrine was identified opportunistically along the Arkansas
River below Kaw Lake on the border between Kay and Osage counties. River otter signs
also were identified opportunistically along the North Canadian River in Mcintosh and
Okfuskee counties near Indian Nation Turnpike bridge. Two sites were searched
opportunistically within the Lower Cimarron Watershed, but no river otter sign was
documented. Middle Washita River and Muddy Boggy Creek watersheds were not
completed because time constraints and high water levels. River otter sign was
documented on Caddo Creek within the Middle Washita River Watershed (Carter
County). River otter sign also was documented at 3 examined sites in the Muddy Boggy
Creek Watershed.
Elk River and Bois D'arc Creek-Island Bayou watersheds were not sampled.
Because the majority ofthe Elk River Watershed occurs in western Arkansas, only one
sample site was selected along the Elk River in Delaware County, Oklahoma, but it was
not examined because water was not present. Bois D'arc Creek and Island Bayou
Watershed, primarily in Bryan County, was not sampled because no suitable sample sites
were located near bridges or access points. All streams within that watershed were small
(i.e., < 1 m) or highly entrenched (i.e., >450 banks). Because streams and rivers tended to
be more entrenched further west, we located fewer suitable sample sites and, therefore,
examined fewer sites in western watersheds. Over 150 sites were removed from the
sample because steep banks dominated the shoreline.
Trackability of negative sites (X = 4.10) and positive sites (X = 3.23) differed (t
= 3.81; P < 0.001). There was no difference (t = 1.79; P> 0.05) between number of
suitable latrine sites located at negative and positive sites. Within positive sites, 56.5% of
12
river otter sign occurred within the first 100 m (X = 93.3 m). Less than 21% oflatrines
occurred after 150 m. Most latrines (59.2%) were located within 50 m ofa transition
between channel habitat variables. Of latrines occurring within 50 m of a stream habitat
transition, approximately 75.6% occurred at a transition between pools (main channel,
comer, lateral scour, and confluence) and other stream habitat types. Most commonly
(74.6%), the transition occurred between pool and riffle (low and high gradient) habitats.
Most latrines were located at the bankfull step (64.3%; Rosgen 1996) along straight
shorelines (53.9%) with vertical (53.8%) or sloped (31.9%) banks. Latrines commonly
occurred near slack water where detritus accumulated within the streambed (33.3%),
areas inhabited by beavers (76.9%), and within 50 m of tributaries (21.2%). The mean
stream width adjacent to latrines was 22.8 m.
Mail surveys.- Twenty-seven percent of 1,153 mail surveys were returned.
Return rates among surveyed groups were 0--46% (Table 1). Thirty-nine percent of all
returned surveys reported observing river otters within the last 5 years (2001-2005).
Twenty-eight percent of all returned surveys reported observing river otter sign within the
last 5 years. Overall, the number of reported river otter sightings and observations of
sign among all groups increased from 22 to 89 and 11 to 62, respectively, during the past
5 years. Survey participants reported river otters in 19 new counties (Fig. 2). State and
federal wildlife employees reported river otters in 6 new counties (Cotton, Marshall,
Okfuskee, Pontotoc, Pottawatomie, and Tulsa). River otter death reports documented
otters in 2 new counties (Okfuskee and Tulsa). Mail survey participants identified all
counties where river otters were captured by APHIS employees except Creek and
Seminole counties. Six new counties were reported by> 1 survey group (Carter,
13
Marshall, Okfuskee, Pontotoc, Pottawatomie, and Tulsa). Locations of river otter
sightings or observance of sign was similar among survey groups. Most sightings and/or
signs occurred in localized areas (e.g., reservoirs) with high accessibility. Mail survey
participants reported river otters throughout all counties identified by sign survey efforts.
Combined, sign surveys and mail survey participants found river otters in 19 new
individual counties (Fig. 2; Caire et al. 1989), and eight ofthose counties were not
identified by sign surveys.
DISCUSSION
Mason and Macdonald (1987) noted a positive correlation (r2 = 0.84; P < 0.01)
between the mean number of scats and the proportion of positive sites from each study
area. Unlike others (Jenkins and Borrows 1980; Kruuk et al. 1986), Mason and
Macdonald (1987) noted that scats can be used to make a broad comparison among
populations. Nevertheless, the validity of using scats to determine otter (Lontra spp,
Lutra spp.) occurrence is still debated (Gallantet al. 2007), but researchers throughout
Europe continue to examine scats and proportions of positive sites to compare otter
densities (Fusillo et al. 2007; MacDonald et al. 2007).
Indirect signs are often effective tools to study wildlife species (Plumptre 2000;
Sadlier et al. 2004; Stephens et al. 2006). However, caution should be used when
interpreting river otter sign data (Rostain 2000; Gallagher 1999) because several factors
can affect detection (Evans 2006, Fusillo et al. 2007); for instance, occupants could be
outside of the sampled area but within its home range. Presence can often be determined,
but absence can be impossible to determine (MacKenzie 2005). Others have reported
14
that there is not always a relationship between number of scats and number of river otters
(Jenkins and Burrows 1980; Melquist and Hornocker 1983; Kruuk and Conroy 1987;
Gallagher 1999; Gallant et al. 2007). Furthermore, sites with less scat could be an
indication of fewer suitable latrine habitats (Romanowski et al. 1996). In contrast, we
determined that no difference occurred between the number of suitable latrine sites at
positive and negative sites.
Because oftime constraints and high water levels, we did not sample Lower
Canadian River and Walnut Creek and Lower North Canadian River watersheds.
However, mail surveys, "death reports," and APHIS records documented river otters
within both ofthese drainages. Sign surveys were conducted within the Little River
Watershed, a tributary to the Canadian River in central Oklahoma. River otter sign was
documented along the Little River in Pottawatomie County and below Lake Thunderbird
in Cleveland County. To reach these locations, river otters must have used the Canadian
River above Eufaula Lake. Within the Lower North Canadian River Watershed, we
collected 1 river otter carcass and identified river otter signs above Eufaula Lake along
the North Canadian River in McIntosh and Okfuskee counties.
We examined 3 sites within the Muddy Boggy Creek Watershed that contained
river otter sign. Most likely river otters have become well established throughout this
watershed because reintroduction efforts (McGee Creek WMA), suitable habitats, and
neighboring watersheds (Clear Boggy Creek Watershed, Kiamichi River Watershed)
contained relatively high proportions of positive sites (Fig. 1).
Mail surveys allowed us to obtain specific locations of river otters throughout
Oklahoma and were relatively inexpensive and required less time and effort than sign
15
surveys; however, data should be interpreted cautiously. Previous researchers surveyed
only natural resource employees because responses from outdoorsman were considered
unreliable (Van Dyke and Brocke 1987; McBride et al. 1993; Pike et al. 1999).
However, even natural resource professionals can be inaccurate when identifying animal
sign unless properly trained (Evans 2006). Within our study, Chi-square analysis
revealed that positive responses among surveyed groups (trappers, ODWC, federal
employees) did not differ ("l = 1.17; df= 2; P> 0.10). Regardless of who is surveyed,
researchers must account for issues regarding access; locations commonly visited by
outdoorsman and areas not accessible could influence distributional data (Stubblefield
and Shrestha 2007). Van Dyke and Brocke (1987) noted that human-based surveys
should not be used alone to describe distribution of mountain lions; instead; such surveys
should be used with other methods to determine spatial distribution. Mail survey
information should only be used as estimates of mammal distribution (Blumberg 1993).
Since the 1970s, river otters have become more prevalent throughout eastern
Oklahoma and continued to spread westward, recolonizing parts of their historic range
(Hatcher 1984; Base 1986). By 1992, APHIS employees reported catching river otters in
6 counties (Atoka, Haskell, Latimer, Leflore, McCurtain, Pushmataha) in southeastern
Oklahoma. Illustrating westward movement, river otters were unintentionally captured in
> 1 new county, on average, each year from 1991 to 2007 (Fig. 3), but the majority of
annual incidental captures by APHIS employees came from southeastern Oklahoma.
Currently, river otters have become well established and commonly occur throughout
most of eastern Oklahoma. Although we documented river otters in central Oklahoma, it
is unlikely that they occur at high densities throughout watersheds west of Blue River,
16
Clear Boggy Creek, and Lower Washita River watersheds and east ofWMNWR. Mail
surveys and APHIS harvest records showed few accounts of river otters in central
Oklahoma. Furthermore, sign surveys within Little River Watershed (central Oklahoma)
showed relatively low proportions of sites containing river otter sign (29%). Similarly,
29% of examined sites along upper portions of the Deep Fork Watershed were positive.
We suggest that no more than broad comparisons among large watersheds should
be made from the proportion of positive sites within a watershed (Macdonald 1987) and
management decisions should not be based solely on sign indices (Gallagher 1999).
Most importantly, sign surveys should be used to monitor sample sites throughout time to
document range expansion and/or reduction (Swimley and Hardisky 2000). Large
reductions in population size may be more evident when baseline data have been
recorded previously. Changes in scat frequency may be detectable only when otter
populations have been impacted greatly (Jenkins and Burrows 1980; Mason and
Macdonald 1987); for example, Lode (1993) used sign-surveys to document otter decline
in France. Sign surveys were used to document range expansion and recolonization in
Poland (Romanowski 2006). Other state wildlife agencies already use sign surveys to
monitor river otter distributions (Boyd 2006, Evans 2006).
Conducting systematic surveys is essential to species management and
conservation throughout time (Elmeros and Bussenius 2002; Gallant 2007) and should be
continued in Oklahoma. Within Oklahoma, relatively large watersheds such as Arkansas
River, Canadian River, Red River, Cimarron River, and Washita River, follow a west-to-east
pattern and facilitate westward dispersal and expansion of river otters. Studies using
indirect sign to examine river otter populations should consider detectability and repeated
17
visits to determine river otter presence or absence (Royle and Nichols 2003; MacKenzie
2005). Observer skill should also be evaluated using standardized methods (Evans 2006).
To achieve greater statistical power, the number of sites throughout each watershed
should be increased. In locations where suitable latrine sites do not exist, European
researchers have created artificial latrine sites to increase effectiveness of monitoring
efforts (Chanin 2003). Chanin (2003) recommended that sign surveys should be
conducted annually for 10 years, and then sampling should occur at intervals of2-3
years. Because sign surveys cannot detect annual fluctuations in river otter populations
(Clark et al. 1987; Gallagher 1999), we recommend visiting sites biennially until
variations (e.g., increase, decrease) cease. As baseline data and populations become
established, sampling intervals can be repeated less frequently.
ACKNOWLEDGMENTS
Funding for this research was provided by the Federal Aid, Pittman-Robertson
Wildlife Restoration Act under Project W-158-R ofthe Oklahoma Department of
Wildlife Conservation and Oklahoma State University. The project was administered
through the Oklahoma Cooperative Fish and Wildlife Research Unit (Oklahoma
Department of Wildlife Conservation, United States Geological Survey, Oklahoma State
University, Wildlife Management Institute, and United States Fish and Wildlife Service
cooperating). This publication was partially supported by the National Science
Foundation Louis Stokes Alliance for Minority Participation Bridge to Doctorate
Program under grant number HRD-0444082. We would like to thank S. K. Davis and A.
A. Foster for their assistance in the field. A special thanks to D. Hamilton from the
18
Missouri Department of Wildlife Conservation and M. Fischer from the Arkansas
Trappers Association for their guidance and training. We also thank R. Thornburg and S.
Sheffert of the Oklahoma Fur Bearers Alliance for their insight and assistance.
Numerous employees of the ODWC provided much needed assistance; we especially
thank A. Crews for helping develop the river otter survey. We thank hundreds of state
and federal employees and private and professional trappers who participated in the mail
survey. We thank hundreds of landowners across eastern Oklahoma who allowed
temporary access to their property. This project was completed as partial fulfillment for
the requirements of the degree of Master of Science.
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